<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>box-sizing</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        span{
            display: inline-block;
            width: 200px;
            height: 200px;
            background-color: orange;
        }
        .one{
            /* 不算padding和border */
            /* box-sizing: border-box; */
            /* padding: 20px; */
            /* border: 5px solid red; */
        }
    </style>
</head>
<body>
    <span></span>
    <span class="one"></span>
</body>
</html>